Many wireless systems such as global positioning systems (GPS), Wi-Fi, Bluetooth beacons and ultra-wideband, and techniques, such as Received Signal Strength (RSS), time difference of arrival (TDOA), angle of arrival (AOA), or time of arrival (TOA) exist to determine the position of a radio-frequency device. Wi-Fi infrastructure is widely deployed and the ability to use this infrastructure for LBS is desirable. Many LBS services require position accuracy of less than one meter. However, this is difficult to achieve in Wi-Fi location systems due to multipath. An additional feature of Wi-Fi is that identity can be determined from media access control (MAC) addresses or other network identity protocols (e.g., internet protocol addresses).
Video camera networks can be used to track people or objects and determine their location. Location accuracy of less than one meter can be achieved using video cameras. Although this position accuracy is important, determining a person or object's identity is required for most applications. Determining identity based on appearance in a video is difficult and prone to error.
Applications requiring the location of wireless mobile devices are referred to as location based services or LBS. These services require the identity of the device and the device's location. A person with a wireless device can be located in several ways. A GPS within their mobile phone can report the user's location. In this scenario, the mobile application queries the GPS and forms a request including their location for the LBS. Unfortunately, GPS has the disadvantage of not working indoors.
Another method to locate the user of a mobile device is to use wireless infrastructure such as Wi-Fi access points to triangulate their location based on radio waves emitted by the device. Three or more wireless receivers record the received signal strength or the angle of arrival of the radio frequency signals from the mobile device. These receivers could be Wi-Fi, Bluetooth, RFID, or other wireless devices. A location server processes the data from these receivers to triangulate the mobile device's location. The application queries the location server for the user's device location. The location server ties the radio waves to the specific person's mobile device using MAC addresses or other network identity protocols. Unfortunately, both GPS and Wi-Fi triangulation frequently cannot give the accuracy necessary for emerging applications, especially for indoor environments with RF multipath.
Another method is to use video cameras to visually determine a person's location. This method has the advantage of being very accurate, however it has a large disadvantage. A video camera system cannot identify which person is making a location based query with their mobile device. Moreover, there is no way for the mobile application to associate itself with a visual based location system; the visual based system can only calculate where someone is, it cannot figure out who they are.